Deny detective inspector’s allegation (8)
I believe the answer is:
disclaim
'deny' is the definition.
(disclaiming is a kind of denying)
'detective inspector's allegation' is the wordplay.
'detective inspector's' becomes 'dis'.
'allegation' becomes 'claim' (I've seen this before).
'dis'+'claim'='DISCLAIM'
(Other definitions for disclaim that I've seen before include "Disown or deny, maybe responsibility" , "Forswear" , "Renounce" , "Deny, refuse to acknowledge" , "Deny or relinquish" .)